Effects of PM2.5 exposure during high bushfire smoke days on birthweight and gestational age in Hunter New England, NSW, Australia. A study on pregnant people who smoke and don't smoke.

Australia's 2019/20 bushfire season was one of the most severe on record, from both land mass burned and the economic impact. This extreme weather season allowed the researchers to examine the effect of high PM exposure during high bushfire days on birthweight and gestational age. It is well known that bushfire smoke is harmful to human health. However, the impact this has on the developing fetus is not yet clear. 25,346 births were assessed, their exposure calculated based on location data, and outcomes analyzed. Mothers exposed to high PM (measured by a 24-hour average PM greater than 25 µg/m) demonstrated a significant birthweight reduction of 0.77 g per day of exposure. Those who were also self-identified as having smoked at any time during their pregnancy were at higher risk, with a 1.33 g reduction in birthweight per day of exposure. Gestational age was reduced by 0.01 days per day of exposure in the total cohort, with no significant difference demonstrated in those who smoked. The compounded effects of high PM exposure may result in birthweight reduction, with neonates born to mothers who smoked at increased risk.